As disclosed in Patent Document 1, various hard-coated cutting tools have been proposed. These rotary cutting tools are coated with a hard coating such as a diamond coating to improve their wear resistance. In recent years, there has been increasing market demand for cutting tools able to cut hard and brittle materials that are difficult to cut such as glass, ceramics and cemented carbide, and many cutting tool manufacturers have been conducting research and development on cutting tools that are able to meet this market demand. In particular, they have been researching and developing cutting tools that typically use super-strong, super-hard cemented carbides as the tool base material, which are coated with a hard coating such as a diamond coating or a nitride-based coating.